Preheat oven to 350 degrees. In a mixing bowl; combine mangoes and lemon juice; set aside. You can either do this next step in the oven, or on a stove top. In an 8-inch baking pan; melt ¼ cup of butter and sugar; stirring until sugar dissolves. Arrange mangoes decoratively in pan. In a mixing bowl; combine egg, oil and buttermilk. Stir in remaining ingredients. Pour batter over mangoes; bake 35-40 minutes. Invert onto serving platter. In a saucepan over medium heat; warm preserves. Brush over top of cake; allow to sit 10 minutes.